Rainbow yawned as she walked down the hall towards her room. She hadn't realized how tired she was. She walked by a window, and paused to admire Luna's beautiful night. The stars were twinkling, and the moon was shining brightly. Rainbow smiled, and then continued walking when she saw a flash of light in the corner of her eye.

Huh? thought Rainbow, looking around. What was that?

"Ouch..." muttered a voice from another room.

Rainbow quietly walked over to the room where the voice had come from, and peeked in. A yellow-orange unicorn with a red and yellow mane stood up shakily in front of a large mirror with purple trim. Rainbow watched silently as her horn flickered, before finally sustaining a dark turquoise glow.

"Perfect..." whispered the unicorn. "Now where is the item I seek?"

Rainbow blinked in confusion as the unicorn stood still with her eyes closed, and her horn glowing. Her horn briefly faded to a darker shade, before winking out. The unicorn opened her eyes, and nodded.

"I see..." she said softly. "It's under the castle..."

At this point, Rainbow simply pushed open the door and walked into the room. The unicorn whipped around and looked at her in surprise,  before casting Rainbow a glare.

"Who exactly are you?" asked Rainbow suspiciously. "And what are you doing in here?"

"Like I need to tell you, rainbow-head." said the unicorn. "Now move out of my way so I can do what I need."

The unicorn's horn flared up threateningly, and Rainbow's eyes narrowed. Her horn lit up bright red in response, and the unicorn smirked.

"What do you think you can do against me?" she asked. "You're just some average unicorn going up against an ultra powerful one!"

"If you'd use your eyes you would see that I'm not just a unicorn." said Rainbow, flaring out her wings. "And I think you're a bit out of the loop. Here, I'll give you some help: I'm Rainbow Dash. Princess Rainbow Dash if you want to be specific."

"Rainbow Dash, huh? That sounds like a pegasus name. You're as deserving of being an alicorn as Cadence: not at all."

Rainbow reacted instantly by flying towards the unicorn, who barely manged to dodge out of the way. She blasted out a beam of dark turquoise magic off at Rainbow, who countered it with a slightly weaker red one. The resulting beams created a small shock wave, which knocked Rainbow's crown off her head. The unicorn instantly picked it up in her magic, and brought it over to look at it.

"Oh, so this must be why you can even use magic!" she said with a smirk. "You've got a magical artifact here! I think that I'm far more deserving of this, thank you very much. Now go fly off while I use this to boost my already amazing power!"

Rainbow grabbed her crown in her magic, and yanked away from the unicorn. The crown froze in midair between the two ponies, one half covered in red magic, the other covered in turquoise.

"Give me that crown..." hissed the unicorn angrily.

"Not a chance!" snapped Rainbow. "Now you drop my crown right now!"

"No way!"

The unicorn dove forward towards the crown, and Rainbow quickly flew towards it. The unicorn grabbed it first, and her horn glowed brightly. However, Rainbow grabbed it just in time for the unicorn to let off her spell. They both crashed down onto the floor of the throne room, and Rainbow realized that the unicorn had tried to teleport away as an escape. The throne room was unfortunately empty, but Rainbow held onto her crown tightly with both her magic and hooves.

"Give me the crown!" yelled the unicorn.

"No!" yelled Rainbow. "Luna! Celestia! There's a thief trying to steal my crown!"

The unicorn glared at Rainbow, and her horn flared brighter. In a flash of light, she had teleported her and Rainbow into the hallway outside the room with the mirror. Rainbow managed to wrench her crown away, and instantly flew down the hall, grasping it tightly with her magic and hooves.

"Get back here!" yelled the unicorn, sprinting after her.

Rainbow didn't respond, and continued flying. She kept glancing back at the unicorn, whose horn was glowing darker and darker turquoise. Her eyes suddenly began to change color, her eyes themselves turning red, her corneas turning green, and a familiar purple haze flowing out. Rainbow's mouth dropped open in shock, just as the unicorn blasted a beam of dark magic off at her. The magic hit Rainbow, sending her sprawling across the ground, and causing her to drop her crown.

"Thanks for the gift, Princess." said the unicorn tauntingly, before running back down the hall towards the room with the mirror.

Rainbow got up and flew after the unicorn, her wings aching from the magic blast. She put on a burst of speed to reach the unicorn just as she entered the room with the mirror, and her crown got knocked away. Rainbow's crown sailed over to the mirror, before going into it. Rainbow's mouth dropped open in shock, and the unicorn grinned.

"What did you do with my crown?!?" yelled Rainbow.

The unicorn teleported over to the mirror, and smirked at Rainbow, against.

"Later, pegasus!" she said, before diving into the mirror.

Rainbow stared for a few seconds, before flying towards the mirror. At that moment, Celestia and Luna both ran up to the doorway, and Celestia quickly grabbed Rainbow in her magic before she could make it to the mirror.

"What happened?" she asked, gently setting Rainbow down on the ground.

"A unicorn stole my crown!" cried Rainbow. "She ran into that mirror with it!"

Celestia's eyes widened in surprise, and her mouth dropped open a bit.

"Sister, what is the matter?" asked Luna.

"The unicorn," said Celestia, "Did she have a yellow-orange coat and a red and yellow mane?"

"Yes!" said Rainbow.

"Then I know who she is: Sunset Shimmer."